This invention relates to a portable radio communication device with improved antenna radiation efficiency. The invention is particularly useful for, but not necessarily limited to, hand held battery powered portable radio telephones.
Portable radio communication devices such as hand held portable radio telephones, often called cellphones, mobile phones or handphones, are becoming a common and convenient form of communication. Users generally desire such communication devices to be compact and therefore battery size is a design consideration. If the battery size could be reduced without compromising talk time then the overall size of battery powered communication devices could be reduced. However, amongst other factors, talk time is dependent upon battery size. It would therefore be advantageous to improve antenna radiation efficiency of communication devices in order to reduce battery size without compromising talk time. Alternatively, if antenna radiation efficiency could be improved, then for a given type battery, talk time could be increased.
In Tay et al (Dipole configuration with strongly improved radiation efficiency for hand-held transceivers, IEEE Transactions on Antennas and Propagation, Vol. 46, pp. 798-806, June 1998) there is described a symmetrical antenna with improved radiation efficiency. The antenna has an associated reflector in the form of a wire. This symmetrical antenna is not ideally suited for portable radio communication devices, which typically use asymmetrical antennas. Further, the wire reflector only operates as a highly localized reflector, with perceived high current densities, and therefore does not provide a significant advantage for use with portable radio communication devices.
According to one aspect of the invention there is provided a portable radio communication device with improved antenna radiation efficiency, said radio communication device comprising:
an antenna asymmetrical about a feedpoint thereof;
a housing at least partially enclosing said antenna; and
an electrically conductive surface providing a reflector for said antenna, said reflector having a length that is at least half a wavelength of an intended lowest operating frequency of said radio communication device.
Preferably, said antenna may have a stub portion extending from said housing.
Suitably, said antenna may have a ground plane portion associated with a circuit board enclosed in said housing, and wherein said feedpoint is between said stub portion and said ground plane portion.
Preferably, said reflector can be electrically floating relative to said ground plane.
Suitably, said reflector may be a conductive plate.
Preferably, said reflector can be disposed on said housing. Alternatively, said reflector may be integrally molded in said housing.
Suitably, said reflector may be disposed on a surface of said housing adjacent a speaker outlet thereof. Preferably, said reflector can be disposed on said surface and at least one side surface of said housing. If required, said reflector can disposed on every side surface of said housing to provide an electrically conductive shell.
In one preferable form, said reflector may be in the form of a meander strip. The meander strip can be configured so that electric field components of said antenna that are induced into said reflector are substantially summed in a direction parallel to a longitudinal of said ground plane portion and cancelled in an transverse axis that is transverse to said longitudinal axis.
Preferably, said reflector is in the form of meander strips having lengths parallel to each other. The meander strips can be suitably configured so that electric field components electric field components of said antenna that are induced into said reflector are substantially summed in a direction parallel to a longitudinal of said ground plane portion and cancelled in an transverse axis that is transverse to said longitudinal axis.
Suitably, said reflector can be a combination of one or more meander strips and at least one conductive plate. In one form, said meander strip and conductive plate may be preferably configured so that electric field components of said antenna are substantially summed in a direction parallel to a longitudinal axis thereof and cancelled in an transverse axis that are transverse to said longitudinal axis.
Suitably, said reflector is may be a conductive plate with one or more apertures therein.
Suitably, said reflector may consist of plurality of parallel conductive plates.
Preferably, the reflector may have a width that is greater than a width of said ground plane portion.